Skip to Content

Register Login

Industry Online Support

Technical Forum

Navigation

Delay or loop

Created by: Maselo at: 6/25/2012 11:37 PM (12 Replies)

Rating (5)

Thanks 5

Result pages:: |; 1 | 2; |

13 Entries

Entries per page: 10 | all

6/25/2012 11:37 PM	Rate (0)
Maselo Experienced Member Joined: 1/12/2011 Last visit: 3/14/2023 Posts: 68 Rating: (0)	Hi, experts! I need to build a 10 ms delay subroutine (ex. CALL FC2) to syncronize with a PROFIBUS (time between out and in response). I tried to use (SS) timer with LABEL and JUMP to keep RLO in the same routine while timer is running. It works, but after some loops the PLCSIM stops! I not tested with a controller. Please, has anybody a good idea? How can I do a loop or a delay subroutine to delay the RLO? Regards!

Suggestion To thank Quote Answer

6/26/2012 9:57 PM	Rate (1)
Zenta Silver Member Joined: 10/12/2006 Last visit: 5/24/2023 Posts: 206 Rating: (25)	Maselo Hi, experts! I need to build a 10 ms delay subroutine (ex. CALL FC2) to syncronize with a PROFIBUS (time between out and in response). I tried to use (SS) timer with LABEL and JUMP to keep RLO in the same routine while timer is running. It works, but after some loops the PLCSIM stops! I not tested with a controller. Please, has anybody a good idea? How can I do a loop or a delay subroutine to delay the RLO? Regards! Hi Maselo, /tf/WW/en/Posts/66145 maybe helpfully Regards Zenta

Suggestion To thank Quote Answer

6/26/2012 10:38 PM	Rate (1)
dchartier Grandmaster-Expert Joined: 9/27/2006 Last visit: 12/3/2023 Posts: 12186 Rating: (2636)	Maselo Hi, experts! I need to build a 10 ms delay subroutine (ex. CALL FC2) to syncronize with a PROFIBUS (time between out and in response). I tried to use (SS) timer with LABEL and JUMP to keep RLO in the same routine while timer is running. It works, but after some loops the PLCSIM stops! I not tested with a controller. Please, has anybody a good idea? How can I do a loop or a delay subroutine to delay the RLO? Regards! Hello Maselo; Would you mind discussing your application a bit, so we may understand why you wish to set a delay for the processor? This is not considered a good practice in a PLC, where you need the processor to cyle through its scan as fast as possible, without delay or snags. Also you have to consider that the Profibus scan is totally asynchronous with the PLC scan, so setting any specific delay would probably not give you synchronisation anyway... Better to think of using coordination signals between the Profibus comms and the CPU program to set events that will coordiante between the two. Regards, Daniel Chartier

Suggestion To thank Quote Answer
This contribution was helpful to 3 thankful Users fritz Zenta Lucky123

6/27/2012 1:07 PM	Rate (1)
Zenta Silver Member Joined: 10/12/2006 Last visit: 5/24/2023 Posts: 206 Rating: (25)	one year ago I made a projekt, with servo drives (not SIEMENS SERVO) this drives hang in profibus and if I gave cmd this servos faster than 10ms the drives stopped :-( and my PLC cycle time is 2ms. So I need a slower cycle time for the correct vorking... so usualy we need a faster cycle time, but not always... regards Zenta (sorry my bad englis)
	Last edited by: Zenta at: 6/27/2012 1:08 PM
Suggestion To thank Quote Answer

6/28/2012 1:24 PM	Rate (0)
Maselo Experienced Member Joined: 1/12/2011 Last visit: 3/14/2023 Posts: 68 Rating: (0)	Hi Maselo, /tf/WW/en/Posts/66145 maybe helpfully Regards Zenta I gave a look there, but I need to test it in my program Many THX!
	Last edited by: Maselo at: 6/28/2012 9:06 PM
Suggestion To thank Quote Answer

6/28/2012 3:21 PM	Rate (0)
Maselo Experienced Member Joined: 1/12/2011 Last visit: 3/14/2023 Posts: 68 Rating: (0)	Hello Maselo; Would you mind discussing your application a bit, so we may understand why you wish to set a delay for the processor? This is not considered a good practice in a PLC, where you need the processor to cyle through its scan as fast as possible, without delay or snags. Also you have to consider that the Profibus scan is totally asynchronous with the PLC scan, so setting any specific delay would probably not give you synchronisation anyway... Better to think of using coordination signals between the Profibus comms and the CPU program to set events that will coordiante between the two. Regards, Daniel Chartier Thx for the reply! I will explain you better. I need to transfer about 480 words to PLC using profibus. This is about 5 times the profibus limit. So, I'm using Prolinx Profibus Gateway with internal memory database paging to tranfer all the data divided in 100 words blocks, sending a command called Raw Database Exchange (from PLC to Gateway profibus output to receive the data from gateway profibus input) in this way (see also the attached file): 1 - Command: Send 100 words to output (6 are mailbox command and 94 are data) from a 100 words DB block 2 - Response: Receive 100 words from input (4 are mailbox control and 96 are data) to a 100 words DB block This will be repeated 5 times (96 x 5 = 480). So, I have to syncronize each time to not get the gateway data from previous 100 words. The better way that I found to syncronize it is just to do a small delay. The program will be in this sequence: - Read DB 1 and move the 100 words data to profibus output - Delay 10 ms - Read the profibus input (the response) and move the 100 words data to DB10 - Read DB 2 and move the 100 words data to profibus output - Delay 10 ms - Read the profibus output (the response) and move the 100 words data to DB20 Repeat to DB 3 (30), 4 (40) and 5 (50). I configured the profibus baud rate to 1.5 M, so will be 3 Mbit/s (out-in) or 0.33 ms by bit (5.33 ms by word). The S7 timer works at least with 10 ms. Please, I appreciate if you have a better idea. PS. The PLC is exclusive, not has IO modules and will be used just to read the profibus input data and send to HMI by profinet. I tried to use SFC14 and SFC 15 function blocks but the PLC got a fault (the limit is 64 words to process image). So, I had to use ID and QD variable addresses. Excuse my poor english... Best regards! Attachment Prolinx Gateway Database Paging.pdf (51 Downloads)
	Last edited by: Maselo at: 6/28/2012 6:40 PM
Suggestion To thank Quote Answer

6/28/2012 10:06 PM	Rate (0)
Maselo Experienced Member Joined: 1/12/2011 Last visit: 3/14/2023 Posts: 68 Rating: (0)	Zenta Hi Maselo, /tf/WW/en/Posts/66145 maybe helpfully Regards Zenta It works for 50 ms but for 10 ms got fault! The CPU cycle is 150 ms. See the objective of the delay routine in the post above. Any idea? Thx again!
	Last edited by: Maselo at: 6/28/2012 10:07 PM
Suggestion To thank Quote Answer

6/28/2012 11:04 PM	Rate (0)
Maselo Experienced Member Joined: 1/12/2011 Last visit: 3/14/2023 Posts: 68 Rating: (0)	Well, guys... I'm trying to test this FC routine. I will not tested with the gateway yet, but it seems to work: TEMP: AN M 100.0 L S5T#10MS SF T 1 NOP 0 NOP 0 NOP 0 A T 1 = M 100.0 A M 100.0 JC TEMP Any idea???

Suggestion To thank Quote Answer

7/1/2012 2:59 AM	Rate (1)
fritz Diamond Expert Joined: 10/7/2005 Last visit: 12/3/2023 Posts: 2997 Rating: (1040)	Hello Maselo I would not want to depend on Timers and/orgeneral delay loops to achieve what your are trying to do as there are the following number of problems associated with thisapproach. 1.) Timer accuray: S5 Timer have a 10ms resolutionand are updated by the OS in the background. Your 10ms Timer and loop could as such become true anytime from immediately up to 10ms. 2.) Let's say you implement a different approach such as looping through a certain amount of "dummy code" perhaps a100 or 200 or whatevernumber tosimple create the desiredlonger scan time. Your logic now heavily depends on the choosen CPU (i.e. the delay will be faster or longer if executed ina different CPU model). 3.) Assumingyou overcome the above mentioned hurdles somehow (e.g. program a self optimising PLC scantime delay by taking OB1's previous cycle time into account), you still have the Profibus update time to deal with. While Profibus is generally deterministic and you will get a DP Slave response for exampleevery 5 ms, there may and can be instances where the DP Slave gateway issues a Diagnostic message instead of a normal response (or does not respond at all in due time etc. etc.). Your time based "sequencer" logic will stillhappily move on to issue the next set of data which is not what you want. In summary: Listen to Daniel Chartier's advise when he said "Better to think of using coordination signals between the Profibus comms and the CPU program to set events that will coordiante between the two". An acknowledgement or handshaking based handlingisthe only way to program robust communciation. In your case, your Gateway seems to echo back the request header information, I suggest you use this to identify that the information has been processed and that you can now move on to issue the next set of data to it. I hope this helps
	Cheers fritz The advice and opinion given in this thread is that of the author and does not necessarily reflect the views of I S Systems Pty Limited. To find out how I S Systems can help you with your automation needs please visit www.issystems.com.au.
Suggestion To thank Quote Answer

7/2/2012 2:25 PM	Rate (0)
Maselo Experienced Member Joined: 1/12/2011 Last visit: 3/14/2023 Posts: 68 Rating: (0)	Dear Fritz, Thanks a lot for your answer! Now I understand why is it better not use a timer. I'm thinking to use a simple loop and the program will be anything like this: 1 - Read DB 1 and move 100 words data to profibus output 2 - Read the profibus input IW 1 (gateway memory address in the header) 3 - If IW 1 is not the address of the first block, jump to 2 4 - Read the profibus input again (the response) and move 100 words data to DB10 5 - Read DB 2 and move 100 words data to profibus output 6 - Read the profibus input IW 1 7 - If IW 1 is not the address of the second block, jump to 6 8 - Read the profibus input again (the response) and move 100 words data to DB20 9-12, 13-16 and 17-20 -> Repeating to DB 3 (30), 4 (40) and 5 (50). 21 - Return to 1 PS. Maybe will be better to do it using function blocks (Call FC1, FC2... FC5). In this example, the RLO will be delayed till it gets the write response in profibus input. Do you have any better idea? The CPU is 412H Regards!
	Last edited by: Maselo at: 7/2/2012 2:29 PM
Suggestion To thank Quote Answer

|

Share this page:

Share this page on...

Follow us on